The broad objective of the proposed project is to gain a more thorough understanding of the production and perception of English fricatives. To date, no single metric has been able to classify place of articulation for all English fricatives with a high degree of accuracy. The proposed research will investigate two recent metrics for classifying place of articulation in fricatives - spectral moments and locus equations. While these metrics have successfully been applied to stop consonants, virtually no work has extended these approaches to fricatives. With appropriate modifications, these metrics seem particularly promising for fricative classification. Performance of these global metrics will be compared to a local metric - spectral peak location. Other properties such as noise duration, noise amplitude, and relative amplitude will also be evaluated in terms of their utility in classifying fricative place of articulation.The general research strategy includes detailed acoustic analyses of natural speech tokens produced by a large sample of speakers. In addition, perception experiments using computer-edited natural speech and synthetic speech will be conducted to help evaluate the accuracy of classification metrics and to investigate the "psychological reality" of these metrics. Finally, experiments are planned to specifically explore the separate contribution of auditory, visual, audio-visual, and contextual linguistic information to the perception of sounds which, it is often claimed, rely primarily on non-acoustic properties. By relating acoustic and perceptual data, and by comparing the role of auditory, contextual, and visual information, the proposed research thus aims at a comprehensive account of the acoustic and perceptual properties of English fricatives. In addition to increasing our general understanding of the normal processes of speech production and perception, this research will have practical benefits, including direct applications to hearing-impaired populations.